1. Field of the Invention
The present invention relqates to a bed device, and to a process for producing polyolefins such as polyethylene and polypropylene using such a device.
2. Related Background Art
Spouted bed devices which employ a spouted bed have the advantage that all the particles, even relatively large particles several millimeters in size that require an excessively high gas velocity for fluidization in a fluidized bed, circulate and are thoroughly mixed. As used herein, “spouted bed” refers to a state characterized by the circulatory movement of particles wherein, under the action of a gas introduced at a high velocity from a gas inlet orifice provided at the bottom end of a cylindrical vessel, there forms a spout (sometimes referred to below as the “spout portion”) which has a dilute particle concentration near the center axis of the particle bed held within the vessel and in which particles flow upward together with the gas, and there also forms at the periphery of the spout an annular particle bed where particles fall in a moving bed state under the influence of gravity.
It is known that there remains room for improvement in spouted bed devices from the standpoint of the solid-gas contact efficiency between the particles and the gas. One means for enhancing the solid-gas contacting efficiency between the particles and the gas while maintaining the excellent mixing properties of a spouted bed, described by K. Takeda and H. Hattori in “Spouted bed device provided with gas outlet in sidewall” (Kagaku Kogaku Ronbunshu 1, No. 2, 149-154 (Kagaku Kogaku Kyokai, 1975), involves providing a gas outlet in the sidewall of the cylindrical vessel in which the spouted bed is formed.